Screen for color photography.



c. L. A. BRASSEUR. SCREEN FOR COLOR PHOTOGRAPHY. APIfLICATlON F |LED MAR. 1.1908.

1,154,607. 7 .PfitentedSept. 28, 1915.

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Specification of Letters Patent.

SCREEN FOR COLOR PHOTOGRAPHY.

Patented sept- 28, 1915.

Application filed March 7,3908. Serial N0. 419,814.

To allwhom it may concern:

Be it known that I, CHARLES L. A. BRAS- SEUR, a citizen of the United States, and a resident of New York city, in the county of New York and State of New York, have invented a certain new and useful Improve-v ment in Screens for Color Photography, of

which the following is a specification.

This invention relates to an improvement upon the apparatus described in my French Patent Number 36 L132, dated March 1,1906, the said improvement being set forth in a certificate of addition No. H68 to said patent dated March 9, 1907, and the invention or improvement consists of means for varying the areas of color-filters in the copyingcamera. The filters in the copying camera are shown in said patent at Figures 13 and 14, and their use is'described in the specification at page 5, but the areas of their sectors are invariable.

It is evident that, if the ,photographic emulsions with which the positive grain or line screens. are coated, had always the same relative sensitiveness to thegdifferent colors, and, if the light used in copying were al ways the same qualitatively, these-screens, once adjusted, could be used indefinitely. But the variations in the sensitiveness of the emulsion and of the quality of the light, being practically unavoidable, these varying factors must be taken into the account.

Fig. 1 is a front elevation of the de vice; Fig. '2 is a top plan view of a modified form of the devices Fig. 3 is a transverse sectional view takengzthrough the device as shownin Fig. 2 upiiii a plane situated above andin horizontally parallel relation to the axis of the same.

According to the preferred form of this invention, I introduce in the lens of the camera, in the plane of the diaphragm or in as close contact thereto as the constructionof the lens will' permit while observing. theoretical requirements, opaque sectors 1- 1" r, to'vary the area of the red sector R,

The object of these sectors is to vary more or less the surface of the colored transparent sectors R G V of the trichromatic screen, and to facilitate thereby the adjustments of surfaces necessary to obtain unity of exposure time for the three colors. These adjustable sectors, r 1' 75 g 9 '0 can be made of leaves, opening more or less as in a fan, such as those shown particularly in Figs. 2 and 3 of the drawing, or can be made of different sized independent pieces (not shown) which can be inserted through slots made in the tube of the lens for that purpose, or any other obvious expedient may be resorted to in embodying the invention in an operative and practical device. The details of the carrier 2 for these sectors can be varied by competent mechanics to suit partic'ular cases.

It will be noted that with my trichromatic color-filter means are provided which vary the light-transmitting area of one or more of the separate colors, as by shutting ofl all light from certain parts of such color or 7 colors or by absorbing the rays transmitted by certain parts of such color or colors.

What is claimed as new is 1. The combination with a trichromatic color-filter, of means for varying the effective area of one or more of the color areas. 2. A sectored trichromatic color-filter, combined with opaque removable sectors for covering and thus varying the effective area of one or more of the sectors of said filter.

3. In combination, a color filter, divided into a pluralityof light transmitting areas, radiating from a common point, each of said areas being colored differently than the other areaspand means for rendering a portion ofany one of said areasopaque, said means being so formed that the ratio between the area of the opaque portion andthelight transmitting area will be constant at diflerent distances from the said common point, whereby the filter, when arranged for any particular condition, may be employed with different sized diaphragms without re-arrangement.

* 4. Incombiuation, a color filter, divided into aplurality of sector shaped areas rediating from a common point, each of said Signed at New York city in the county areas being colored difi'erently than the other of New York and State of New York this areas, and sector shaped members for varysixth day of March A. D. 1908.

ing the effective area of any of said areas, CHARLES L. A. BRASSEUR. sa d sector shaped members radiating from Witnesses: sald common point when in operative posi- HUGO Moon,

tion. R. W. BARKLEY. 

